The 28-year-old alleged victim, who cannot be identified for legal reasons, had been working in Mr Evans’s office while completing a politics degree when he claims he was the victim of a sexual assault.

He told the court he had been staying at the MP’s constituency home in Pendleton, Lancashire in 2009 when the incident occurred.

He explained that after a night of heavy drinking he had been asleep on the sofa when he awoke to find Mr Evans with his hand inside his boxer shorts.

“I immediately pushed Mr Evans and I shouted, I think it was along the lines of ‘What the F do you think you are doing?” he said.

He told the court that he had confided in the politician about sexual abuse he had suffered as a youngster and felt Mr Evans’s actions had been a “particular betrayal”.

But he said when the matter was referred to the Chief Whip he had been disappointed by his attitude.

“Mr McLoughlin’s was one of mainly irritation. He sighed and huffed the whole time. He said ‘so what do you want to happen now? My response was that that I thought Mr Evans should resign, from his seat as an M, I think I said immediately.

“Mr McLoughlin said ‘it could not be done, the timing is not right, I would find it very difficult to explain why an MP is leaving his seat at this point before a General Election.”

The alleged victim explained how Mr McLoughlin said the unmarried MP could not say he wanted to spend more time with his family.

But the witness said John Randall, who was the Deputy Chief Whip and was also at the meeting, had been more sympathetic and appeared “genuinely concerned” about what had happened.

The alleged victim said he recommended that Mr Evans receive help to come to terms with his sexuality and also his drinking, describing him as a “high functioning alcoholic” who drank heavily everyday.

The witness told the court: “It was suggested I should take some time off from the office, Mr Evans would be heavily sanctioned by the Whips’” he said.

He said it was also agreed that if Mr Evans was caught drinking on the parliamentary estate, he would be escorted off the premises by the Whips.

But he said in time it became clear that what had been promised was not being delivered because Mr Evans was drinking again and there was no sign of any counseling.

Earlier the court heard how Tory MP Conor Burns was warned he would be treated as a reluctant witness if he did not provide a statement to police about an earlier alleged incident.

The MP for Bournemouth West said Lancashire Police had persistently asked him to provide a statement about an alleged assault that took place in 2003, despite him twice telling them he did not have a clear recollection of what had happened.

Mr Evans allegedly indecently assaulted a young Party agent by twice trying to put his hand down his trousers during a function at the Conservative Conference in Blackpool.

Mr Burns, who was a prospective parliamentary candidate at the time, had warned Mr Evans he was drunk and told him to go to bed.

He said Lancashire Police had contacted him last July, following Mr Evans’s arrest on suspicion of rape, requesting a statement, but he had told them he could not remember the event clearly enough to provide a witness statement.

He told the court: “I did not feel my recollection was robust, strong or clear enough to provide a meaningful statement to aide them in their enquiries.”

But he said he was warned he would brought before a judge and treated as a reluctant witness if he did not agree.

He told the court: “They said if I would not give a statement I would be required to appear before a judge, come to court and be a reluctant witness. I felt very uncomfortable about that.”

Another witness to the incident claimed he had seen the alleged victim “thrashing around very violently” with the MP’s hand down the front of his trousers.

Mark Formosa, a former Tory councilor said he had been in a bar at the Imperial Hotel one evening during the conference when he had became aware of a “fracas” involving two men.

He told the court: “I saw the younger man thrashing around very violently from side to side trying to wrench himself free from Mr Evans' grip. Mr Evans had his hand down the front of his trousers and was maintaining his grip and it seemed obvious that the younger man was not able to get him off him.

"I intervened along with several others in order to assist the younger man to get Mr Evans off him. We pulled him off and pushed him back towards the bar."

Mr Evans, the MP for Ribble Valley, is accused of two counts of indecent assault, six of sexual assault and one of rape.